.content{
    width: 640px;
    height: 640px;
    margin: 100px auto;
    position: relative;
}
.btn{
    width: 100%;
    height: 100%;
    position: absolute;
    left: 0;
    top: 0;
    background-color:rgba(0, 0, 0, 0.3) ;
    z-index: 5;
}
.btn button{
    background: none;
    border: none;
    background-size: 100% 100%;
    cursor: pointer;
    outline: none;
    position: absolute;
    left: 50%;
    top: 50%;
}
.startBtn button{
    width: 200px;
    height: 120px;
    background-image: url(../img/start.png);
    margin-top: -60px;
    margin-left: -100px;
}
.pauseBtn{
    display: none;
}
.pauseBtn button{
    width: 70px;
    height: 70px;
    background-image: url(../img/pause.png);
    margin-left: -35px;
    margin-top: -35px;
}
/* sanake */
#snakeWrap{
    position:relative;
    width: 600px;
    height: 600px;
    background: #225678;
    border: 20px solid #7dd9ff;
}
.snakeHead{
    background-image: url(../img/head.png);
    background-size: 180px 266px;
    background-repeat: no-repeat;
    background-position: -145px -139px;
}
.snakeBody{
    background-image: url(../img/body.png);
    background-repeat: no-repeat;
    background-size: 180px 266px;
    background-position: -54px -123px;
}
.food{
    background-image: url(../img/food.png);
    background-repeat: no-repeat;
    background-size: 180px 266px;
    background-position: -56px -195px;
}